10 



THE BEE-KEEPERS' REVIEW. 



the end of the tube. If. the instrument is 

 inverted close to the ear, and the hearing is 

 acute, a slight click or thud will be heard 

 when the mercury comes down against the 

 glass if there is no air. But if air is present, 

 it will act as a cushion under the mercury, 

 and there will be no sound. By placing the 

 instrument in melting snow the correctness 

 of the mark for the freezing point may be 

 tested, and by placing it in boiling water it 

 may be seen whether the boiling point is 

 correctly marked. For the 180° between 

 these two points there is no way to test the 

 accuracy of the grading of the scale except 

 by placing the instrument side by side with 

 one which has been verified and a list of 

 corrections made. Toronto dealers get in- 

 struments tested, and corrections furnished, 

 at the Observatory there for fifty cents each. 

 Owing to the difficulty of making the diame- 

 ter of the tube the same all through, nearly 

 all instruments require correction in differ- 

 ent parts of the scale. There are makers 

 now who turn out instruments which do not 

 vary at any place more than three tenths of 

 a degree. But often cheap instruments vary 

 in places as much as three degrees. By 

 placing the verified instruments side by side 

 with the one to be tested in hot water, and 

 gradually cooling it by adding snow or 

 pounded ice, and making notes of the read- 

 ings at least as often as every ten degrees, a 

 scale of corrections may be made to be used 

 when taking readings. The importance of 

 strict accuracy will become apparent when 

 ascertaining the percentage of saturation. 

 The bulbs of the two instruments selected 

 should be of the same size. A cylindrical 

 bulb is more sensitive than a spherical one, 

 because the surface exposed, in proportion 

 to the whole quantity of mercury, is greater. 

 The bulb of one of the instruments should 

 be covered with thin gauze, it cannot hardly 

 be too thin. For a fountain a glass ink bot- 

 tle will do very well, but if a perforated 

 cork is inserted it will be still better, because 

 dust will be better excluded and more evapo- 

 ration prevented. By tying loosely a piece 

 of candle wick above the bulb, and inserting 

 the other end in the fountain, the gauze on 

 the bulb will be kept moist. The object at 

 all times should be to keep the bulb covered 

 with a mere film of water. In the upper 

 part of a warm room of a dwelling, in very 

 cold weather, a full sized wick will be none 

 too much, because the evaporation is then 

 very great, but the same wick in a bee cellar 



will probably carry up water faster than it 

 will be evaporated, in consequence of which 

 a drop will be found suspended from the 

 bulb. When such is the case the reading 

 will not be strictly correct. A lighter wick 

 should be used when the air is damp. The 

 thermometers should be suspended on a 

 board about midway between the floor and 

 ceiling of the cellar. When taking readings, 

 keep the eye on the same horizontal plane 

 as the top of the column of mercury. If the 

 instruments are sensitive the heat of the 

 lamp may affect them. 



In your editorial referred to you have ex- 

 plained the matter sufficiently as far as you 

 have gone, but a table is necessary to ascer- 

 tain the percentage of saturation. As such 

 tables are seldom called for, I had difliculty 

 in obtaining one, and as you may find a 

 similar difficulty, I have taken the trouble to 

 copy my table for you. I find a reference to 

 Hygrometrical tables, adapted to the use of 

 the dry and wet bulb thermometer, by James 

 Glaisher, F. R. S., London : Taylor & Fran- 

 cis, sixth edition, 1870. This work may be 

 ordered through any bookseller, and prob- 

 ably contains everything required. 



I am pleased to find that you are taking up 

 the subject of moisture in the air as a factor 

 in safe wintering. It used to be a hobby 

 of mine, and later observations have con- 

 firmed the opinions I advocated some years 

 ago. I shall watch your observations with 

 interest. 



[Friend Cornell, in a neatly ruled book, 

 very carefully copied the table showing the 

 perceniage of moisture from 32° with the 

 wet bulb up to 104°, with the difference be- 

 tween the wet and dry bulbs from 1° up to 

 29°. I do not give the table entire, simply 

 that portion that would be likely to be need- 

 ed in determining the percentage of mois- 

 ture in a bee cellar. As the percentage of 

 moisture is always 100 (complete saturation) 

 when the wet and dry bulb thermometers 

 show the same readings, I have omitted that 

 column and commenced with the column 

 when the difference between the thermome- 

 ters is 1°. — Ed. J 



TABLE FOK FINDING THE EELATIVE HUMIDITY 



(OB PEECENTAGE OF SATUBATION) AT ANY 



MOMENT, BY SIMPLE INSPECTION. 



Rule — Note the difference between the 

 readings, and find the relative humidity at 

 the intersection of the line of the wet bulb 

 reading, and the column headed "Differ- 



